Optimized methods for detecting Salmonella Typhi in the environment using validated field sampling, culture and confirmatory molecular approaches
File(s)
Published version
Author(s)
Type
Journal Article
Abstract
Aims
This study evaluated detection methods for Salmonella Typhi (S. Typhi) in the environment, to establish a novel pathway from field sampling to isolation of viable organisms and molecular confirmation from complex environmental samples, thus enabling environmental surveillance of typhoid.
Methods and Results
Multiple media were assessed using clinical isolates from the Public Health England's (PHE) Culture collection. The culture pathway selected consisted of a primary 2% bile broth and secondary Selenite F broth, followed by modified Chromogenic Agar for Salmonella Esterase (mCASE). A qPCR assay was adapted from a validated S. Typhi PCR panel for confirmation of isolates, with comparison to biochemical and serological tests showing good specificity. Sampling locations in Blantyre, Malawi were used to compare sampling methods. Viable S. Typhi were isolated from a mixture of trap and grab river water samples on six occasions.
Conclusions
Culture of viable S. Typhi from environmental samples was possible using effective capture and culture techniques.
Significance and impact of study
Whilst several studies have attempted to detect S. Typhi from the environment, this is the first successful attempt to isolate the organism from river water since the 1980s. Supplementing clinical data with environmental screening offers the potential for enhanced surveillance, which might inform interventions and assess vaccination programmes.
This study evaluated detection methods for Salmonella Typhi (S. Typhi) in the environment, to establish a novel pathway from field sampling to isolation of viable organisms and molecular confirmation from complex environmental samples, thus enabling environmental surveillance of typhoid.
Methods and Results
Multiple media were assessed using clinical isolates from the Public Health England's (PHE) Culture collection. The culture pathway selected consisted of a primary 2% bile broth and secondary Selenite F broth, followed by modified Chromogenic Agar for Salmonella Esterase (mCASE). A qPCR assay was adapted from a validated S. Typhi PCR panel for confirmation of isolates, with comparison to biochemical and serological tests showing good specificity. Sampling locations in Blantyre, Malawi were used to compare sampling methods. Viable S. Typhi were isolated from a mixture of trap and grab river water samples on six occasions.
Conclusions
Culture of viable S. Typhi from environmental samples was possible using effective capture and culture techniques.
Significance and impact of study
Whilst several studies have attempted to detect S. Typhi from the environment, this is the first successful attempt to isolate the organism from river water since the 1980s. Supplementing clinical data with environmental screening offers the potential for enhanced surveillance, which might inform interventions and assess vaccination programmes.
Date Issued
2022-02-01
Date Acceptance
2021-07-08
Citation
Journal of Applied Microbiology, 2022, 132 (2), pp.1503-1517
ISSN
1364-5072
Publisher
Oxford University Press (OUP)
Start Page
1503
End Page
1517
Journal / Book Title
Journal of Applied Microbiology
Volume
132
Issue
2
Copyright Statement
© 2021 The Authors. Journal of Applied Microbiology published by John Wiley & Sons Ltd on behalf of Society for Applied Microbiology This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
License URL
Identifier
https://www.ncbi.nlm.nih.gov/pubmed/34324765
Subjects
Identification
Malawi
Moore swabs
PCR (polymerase chain reaction)
bile broth
biofilm
biofilms
mCASE
river water
salmonella
selenite broth
typhoid
water
Humans
Real-Time Polymerase Chain Reaction
Salmonella
Salmonella typhi
Specimen Handling
Typhoid Fever
Publication Status
Published
Coverage Spatial
England
Date Publish Online
2022-02-01